1. Field of the Invention
The present invention relates to an automotive display apparatus in which a display image of an indicator installed in a dashboard is directed toward a windshield through an opening formed in a dashboard, which windshield in turn reflects the image toward a driver's viewing point so that the driver can see a virtual image of the indicator display at a location in front of the windshield.
2. Prior Art
Automotive display apparatuses of the type in which a display image of an indicator is directly viewed are generally used. In these apparatuses, an indicator is located on the driver's side of a dashboard for providing information on vehicle running conditions. A drawback to these apparatuses is that the driver must largely shift his eyes each time he checks the display of the indicator, resulting in the driver interrupted in seeing the outer field ahead of the vehicle. Especially when driving at a high speed, a driver looks far ahead, and thus the amount of focus shift of the driver's eyes becomes correspondingly large.
With a view to reducing the amount of focus shift of the driver's eyes when he checks the display, a head-up display apparatus has been proposed and put in use. FIG. 3 shows one example of such a head-up display apparatus. This apparatus comprises an indicator 1 such as a fluorescent display tube installed in a dashboard 3 with its display surface directed upwardly. The light from the display of the indicator passes through an opening 3a formed in the dashboard 3 and is reflected by a reflection-treated reflective surface 2a on the windshield 2 toward a driver's viewing point 6 so that the driver can see a virtual image X of the display at a location in front of the windshield 2 in an overlapping manner with the outer field. In the figure, denoted 5 is a bonnet.
A vehicle is generally further provided with a defroster for evaporating and removing the frost (moisture) adhering to the inner surface of the windshield to secure a clear forward view. In the case of a head-up display apparatus such as that mentioned above, in which the surface of a windshield is used as a reflective surface for light from the display of an indicator, a defroster is especially needed. This is because frost on the windshield not only deteriorates a forward view, but also hinders the driver's viewing the virtual display image of an indicator. Thus, as shown in FIG. 3, hot air is led to the opening 3b through the duct 4 and blown therefrom at the surface of the windshield 2 to evaporate the frost thereon.
In addition, JP Utility Model Application Laid-open Specification No. 56080/1985 proposes a head-up display apparatus in which the indicator displaying information on vehicle running conditions is constituted by a light-transmission type liquid crystal display element. In this apparatus, the air having been used to cool the light source is introduced into a defroster duct to make use of the air to defrost the windshield.
In either case, however, two openings are formed in the surface plate of the dashboard, one being an outlet opening of the defroster duct and the other for allowing display light to pass therethrough. This results in restrictions on where to install the indicator. For example, when the forming location of a virtual image is desired to be changed so that the driver's line of sight is shifted from 6a to 6b as shown in FIG. 4, since the angle at which the windshield is provided is predetermined in accordance with the vehicle's model, it is necessary to change the location of the indicator. Moving the indicator to a forward position, however, is impossible, prevented by a wall of the duct.
Further, the surface of an indicator is apt to gather dust, frost and the like, resulting in distortions in the virtual display image. Provision of a transparent glass plate or the like over the display surface of the indicator, e.g., at an opening of the dashboard would involve the troublesome work of wiping the dust, frost and the like off the plate each time when necessary.